In recent years carrier networks use tunneling techniques to separate traffic from users or different services from each other in case the traffic is transported over access and aggregation networks. This prevents network nodes from shortcutting traffic, i.e. the network nodes are prevented to get a shorter way for the traffic. Furthermore, such tunneling techniques neither allow access to traffic on intermediate nodes nor to break out traffic at intermediate nodes between tunnel endpoints.
For example, devices being attached to a node A want to communicate with devices being attached to a node B. As depicted in FIG. 1, the tunnel will be set up between the nodes A and B functioning as tunnel endpoints. Then, any intermediate node between node A and node B will only be able to read the tunnel header that is added at the first tunnel endpoint being represented by node A. At the second tunnel endpoint being represented by node B, the tunnel header will be removed.
Thus, nodes in between are only able to be made aware of the service that is transported if any of this information is incorporated and/or copied into outer headers that these intermediate nodes are able to decode. Unless in case of using header fields with large value ranges, e.g. stacked VLANs or MPLS labels, this method is very limited and requires a mapping function at both ends.
Another alternative is a Deep Packet Inspection (DPI) function. A DPI function inside an intermediate node may also allow decoding the inner headers of a data packet. With state of the art technology, e.g. according to Kevin Roebuck, “Deep Packet Inspection (Dpi): High-Impact Strategies—What You Need to Know: Definitions, Adoptions, Impact, Benefits, Maturity, Vendors”, 2011, an intermediate node has to detect a data packet with a DPI-like function and has to decapsulate the tunnel header in order to decode the whole data packet. The intermediate node has to add the appropriate tunnel header back again in order to insert a data packet into the tunnel.
With regard to the OpenFlow paradigm, as described for example in McKeown et al. “OpenFlow: Enabling Innovation in Campus Networks”, ACM Computer Communication Review, Vol. 38, Issue 2, pp. 69-74, 2008, tunnels can be virtual in a sense that each network node gets configured with a mapping rule to identify any kind of data packet as being part of a tunnel.
Thus, as an example, such a tunnel may be characterized by the tunnel endpoint identifier (TEID), IP address and port number in case of a GTP (GPRS Tunneling Protocol) tunnel in a 3GPP (3rd Generation Partnership Project) mobile core network or by the PPP session ID in case of PPPoE (Point-to-Point Protocol over Ethernet). Though, sessions can be treated individually, but tunnel headers have to be removed and added at each network node. Hence, tunnel header overhead is still involved and results in wasting bandwidth in networks, in particular regarding redundant tunnel headers in long range DSL access loops or microwave mobile backhaul.